A marine security officer, right, works the gate Wednesday at the Port of Portland's Terminal 6.Motoya Nakamura/The Oregonian

Operations at Portland's international container terminal, a workhorse of Oregon's economy, appear increasingly tenuous as a third labor conflict surfaces and big customers waver.

Little-known contract talks between the Port of Portland and the terminal's security guards, represented by the longshore union, reenter mediation Friday. A breakdown in the talks, which have dragged on since July 1, could disable not only the troubled container yard but two other Port terminals.

Separately, contentious contract talks continue with a federal mediator between the longshore union and owners of Northwest grain terminals. The grain talks and the security-guard negotiations are distinct from yet another, better known dispute that broke out last summer involving work with refrigerated containers.

Because of the container dispute, big importers including retail giant Fred Meyer, frustrated by slow operations, are beginning to explore moving shipments to Puget Sound ports. In Fred Meyer's first public comment since that dispute arose, a spokeswoman said Wednesday the company was contemplating strategies should the Hanjin shipping line stop calling on Portland's Terminal 6.

Spokeswoman Melinda Merrill said Freddy's, which brings in more containers from Asia than anyone else at T-6, probably wouldn't have to spend more on trucking imports from Tacoma to Portland, considering the current expense of shipping them 100 miles up the Columbia River. But she said managers realize that leaving the Port of Portland would damage Oregon's economy, on which Fred Meyer sales depend.

"We're not rattling our saber and saying, 'Hey, we're going to move our imports up to Seattle,'" Merrill said. "But I don't think people realize how intricately tied our economy is to having the ability to import so Oregon companies can export."

Fred Meyer and other importers bring in a stream of inbound containers to Portland that then become available at attractive rates for Oregon exporters, whose sales support thousands of jobs across the state. Oregon's only container terminal also has an annual longshore payroll of more than $20 million, which ripples through the area's economy.

Until now, labor problems at the Port have stemmed from claims by the International Longshore and Warehouse Union for the equivalent of two jobs held by union electricians, who plug, unplug and monitor refrigerated containers. Amid the bitter dispute, trucks have backed up outside the terminal, ships have bypassed Portland, cargo has been stranded and a federal judge has issued an injunction banning longshore slowdowns.

But Bill Wyatt, Port of Portland executive director, told Port commissioners Wednesday a strike is possible if the separate talks break down with representatives of 25 marine security officers in longshore Local 28.

Port officials didn't speculate on what would happen in that case at Terminals 6, 4 and 2, where the officers work. But the other longshoremen at those terminals might then walk out in an action that could escape the terms of U.S. District Judge Michael Simon's ban.

The Port's terminal operator, ICTSI Oregon Inc., has indicated it might have to wind down operations at Terminal 6. If ICTSI left, Wyatt said Wednesday, the yard might never reopen as a container terminal.

The longshore union broke weeks of silence Wednesday, responding to questions from The Oregonian with a statement blaming ICTSI for mismanagement. Leal Sundet, a coast committeeman for the union, said in the emailed statement that longshore workers are invested in the region's wellbeing and have toiled for decades to make the Port productive.

Sundet blamed ICTSI for truck backups on North Marine Drive, which extended Wednesday again for as much as a mile.

ICTSI has at times closed terminal gates and invited journalists to film the resulting line of trucks, he said. The company also gets the Port to hire insufficient security during meal hours, he said, creating backups falsely attributed to longshore slowdowns.

"ICTSI Oregon Inc. has made no profits from its operation at Terminal 6," wrote Elvis Ganda, the company's chief executive officer. "Instead it is suffering substantial losses caused by the ILWU's continuing course of slowdowns, work stoppages, gimmicks and hard-timing."

The union is suing Port commissioners for voting to reduce ICTSI's losses by waiving as much as $4.7 million of the company's rent. Wyatt said Wednesday that the Port may consider extending its so-called cost-sharing agreement with ICTSI beyond year's end.

Also at year's end, ICTSI's contract with the Hanjin shipping line will expire, creating additional uncertainty. The companies are negotiating a new contract, with each under pressure from escalating costs.

Hanjin and other shipping lines calling on Portland face mounting claims -- now totaling $728,000, according to ICTSI -- filed by longshore locals that bill for lost wages each time electricians work with the refrigerated containers.

All parties anxiously await a ruling by Judge Simon, who has been asked by National Labor Relations Board attorneys to find the union in contempt of court and stop it from allegedly coercing the shipping lines.